It is with a certain dread every autumn that some companies described by Amazon.com Inc. as its technology partners gather at a Las Vegas convention and find out if Andy Jassy has new plans to encroach on their turf.
These firms run their software on Amazon’s vast array of servers—part of what is known as “the cloud”—and from there sell use of their programs to others. Over nearly three hours, the boss of the Amazon Web Services unit walks the stage, revealing a road map of brand-new features Amazon itself plans to offer,...